S H 

155 

■YW\ 

A NEW PRINCIPLE OF AQUICULTURE 
AND TRANSPORTATION OF LIVE FISHES 



From BULLETIN OF THE BUREAU OF FISHERIES, Volume XXVIII, 1908 
Proceedings of the Fourth International Fishery Congress Washington, 190S 




%■ •?+ WASHINGTON : 



GOVERNMENT PRINTING OFFICE :::::: 1910 




Oass S-H-LffSL 

Book J$H- 



A NEW PRINCIPLE OF AQUICULTURE 
AND TRANSPORTATION OF LIVE FISHES 

From BULLETIN OF THE BUREAU OF FISHERIES, Volume XXVIII, 1908 
Proeeedi?igs of the Fourth International Fishery Congress : : Washington, ipoS 







WASHINGTON :::::: GOVERNMENT PRINTING OFFICE 



1910 



V 






BUREAU OF FISHERIES DOCUMENT NO. 676 
Issued April, 1910 









A NEW PRINCIPLE OF AQUICULTURE AND TRANSPORTA- 
TION OF LIVE FISHES 

By A. D. Mead, Ph. D. 

Member Rhode Island Commission of Inland Fisheries 



Paper presented before the Fourth International Fishery Congress, 
held at Washington, U. S. A., September 22 to 26, 1908, and 
awarded the prize of two hundred dollars in gold offered by 
the United States Bureau of Fisheries for a report describing 
the most useful new and original principle, method, or apparatus 
to be employed in fish culture or in transporting live fishes 



759 



CONTENTS. 

Page. 

Essential features and development of the method 761 

Adaptation to fishes and other pelagic forms 763 

Requirements 763 

Requirements satisfied 764 

Adaptability of the method 765 

Apparatus 767 

General description 767 

Details of structure 768 

Possibility of variation 772 

Precautions 772 

Tests of efficiency 773 

General application of the method in aquiculture 779 

Application in transportation of live fishes 780 

760 



Bul. U. S. B. F., 1908. 



Platk XC. 




Fig. 1. — Floating laboratory and rearing plant from the port side. The forward (left) house 
serves as a laboratory and the after one as the engine house and tool room. Most of th<_- 
rearing cars are covered with white awnings. 




of the plant from the outer rear corner. In foreground one of the cars 

shows the- propeller shaft and faint indication of propeller blades in the water. 



A NEW PRINCIPLE OF AQUICULTURE AND TRANSPORTA- 
TION OF LIVE FISHES. 



By A. D. MEAD, Ph. D., 

Member Rhode Island Commission oj Inland Fislteries. 

J* 
ESSENTIAL FEATURES AND DEVELOPMENT OF THE METHOD. 

The method and apparatus herein described as a novel and practical method 
of fish culture have gradually developed through eleven years of continuous 
experimentation at the marine station of the Rhode Island Commission of 
Inland Fisheries. It may be said, indeed, that the method and the station have 
developed together. The aim has been throughout to provide as simply as 
possible the essential features of the natural environment, biological and physical, 
for aquatic animals while kept in confinement, and to introduce as little as possible 
the unnatural features which are frequently considered necessary in artificial 
culture. Upon this principle there has been sought a feasible method of pro- 
viding water agreeable to the particular species in regard to the various com- 
ponent salts, well aerated but not over aerated, having the proper temperature, 
density, and current, and containing appropriate food in available condition; 
while providing at the same time for the elimination of waste products of animal 
respiration, and avoiding the dangerous chemical and bacterial impurities 
almost invariably present where the water is passed through systems of piston 
pumps, closed conduits, and storage tanks, and is aerated by means of forced air. 

The first step in the development of the method was a very direct and 
simple concession, namely, that of going to the ocean instead of trying to bring 
the ocean into a house on land. The floating laboratory and hatchery was 
therefore adopted as a feasible method of circumventing, if not surmounting, 
many difficulties. 

During the first and second seasons of work it was clearly demonstrated 
that the starfish {Asterias jorbesii) could be reared in the course of the summer 
(four months) from the larval stage to over 50 millimeters measured from 
mouth to tip of arm (nearly twice the length of sexually mature specimens 
captured in June, the breeding season, and therefore a year old), in cars of 

761 



762 BULLETIN OF THE BUREAU OF FISHERIES. 

appropriate shape floating in the water between the pontoons of the houseboat. 
In this case living food was supplied at first in the form of small barnacles which 
had set on boards, and later, as the starfishes grew larger, clams, oysters, and 
mussels were given them to eat. The conditions in these cars were completely 
adequate for the healthy life of these slow-moving animals, and were abnormal 
only in that the young starfishes were protected from their enemies (excepting 
always their cannibal brethren) and were better fed than they often are under 
natural conditions. In many cases where they were especially well fed they 
far outstripped in rapidity of growth individuals found along the shore. They 
throve splendidly and were perfectly healthy. 

This way of raising starfishes may hardly be dignified by the term " method," 
and yet the better condition of these specimens as compared with those usually 
seen in an aquarium — even in an aquarium where many fishes live for a long 
time — is a striking fact. It suggests also that there is often something the matter 
with aquarium water which, whatever the cause, makes it unsuitable for the 
rearing of very sensitive animals. 

At the floating laboratory, animals with the burrowing habit can also be 
kept confined and protected and under constant observation by simply putting 
them into a box of sand suspended in the water. Specimens of the soft-shell 
clam (Mya arenaria) may in this way be very successfully and rapidly reared, 
and they give everv indication of being in a perfectly normal environment. 
Indeed, in our experiments, when they were kept just under the surface of the 
water and in the tidal current, they grew more rapidly than in the most favorable 
shore locality I have ever seen. In one experiment with clams ranging from 5 
to 17 millimeters the increase in bulk during five weeks and two days was 1,861 
per cent. 

In the case of sessile animals like oysters, Crepidula, Anomia, Molgula, 
Botryllus, sea anemones, tubiculous worms, etc., and of those which spin a 
byssus, like the mussel, young clams, and pectens, it is only necessary to provide 
the proper surface for them to set on and protection from predatory animals. 
In case of the hatching of such eggs as those of the flatfish, Menidia, Fundulus, 
and the lobster, with which we have had experience in the course of our opera- 
tions, it would seem that the term "hatching" could hardly be used in a transi- 
tive sense, for, if the eggs are provided simply with water of proper constitution, 
temperature, and conditions for respiration, the eggs inevitably hatch them- 
selves. These nonpelagic eggs, in fact, belong to the same category as the 
sessile or slow moving animals and may be treated accordingly. The method 
of stripping and swirling lobster eggs has been given up with us and instead the 
ripe-berried hen-lobsters are allowed to crawl about in the rearing cars with the 
result that the eggs hatch most satisfactorily. Similarly the eggs of the flatfish 
(Pseudopleuronectes) were hatched with almost no loss by placing them on a 



A NEW PRINCIPLE OF AQUICULTURE. 763 

piece of scrim which formed the bottom of a box about 6 inches deep floated on 
the top of the water in a protected pool. The eggs of Menidia and Fundulus 
are hatched successfully by practically the same treatment. 

ADAPTATION TO FISHES AND OTHER PELAGIC FORMS. 
REQUIREMENTS. 

In the development of the method of fish culture with which our station 
is identified the installation of a laboratory directly upon the water and the 
confining and rearing of animals in cars placed in the water marked the first 
step. For many animals of the types we have mentioned, the slow moving, 
or creeping, the burrowing, and the sessile animals, this is all that is necessary 
for rapid and healthy growth. For pelagic animals, however, like the young 
of most fishes and the larval forms of Crustacea and other marine invertebrates, 
it is not sufficient. The very peculiarities of structure and instinct which adapt 
these creatures to their pelagic life make it difficult to confine them for a long 
time even in relatively large inclosures of the water in which they normally live. 

One is baffled now by one peculiarity and now by another. The larvae 
or fry are often strongly heliotropic, and in going toward or away from the 
light soon strike the boundary wall of their confine, and when they are numerous, 
as they must be in practical culture, die from the effects of crowding, if, indeed, 
they are spared to this fate by their cannibalistic comrades. Often in the 
blind struggle to go toward the light regardless of the boundary wall, they grad- 
ually work their way to the bottom and become entangled in debris or covered 
with silt. 

If, for the sake of good circulation of water, the tidal current is allowed to 
pass through the car, as in the case of sessile or bottom-living forms, the pelagic 
fry are apt to be swept against one side, or to collect in eddies, with disastrous 
results. If, on the other hand, the current through the inclosure is not supplied, 
the water becomes stagnant and not well aerated, and since the time required 
to rear most animals to a considerable size is long, the stagnation under these 
circumstances is almost inevitable. 

The minuteness of many larval animals constitutes a fourth difficulty, for 
perforations or meshes large enough to permit sufficient circulation frequently 
permit also the escape of the fry, while meshes too small for the fry to go through 
become clogged with silt and do not allow free circulation. 

The fifth difficulty in the rearing of pelagic fry in inclosures of this kind 
depends upon the fact that normally they capture their prey "on the fly." 
A dilemma presents itself: If the fry are fed upon smaller animals or plants, 
these too must be pelagic, involving all the difficulties over again, while, if 
artificial food is used, there is no provision for keeping it in suspension, in which 
condition onlv would it be available. 



764 BULLETIN OF THE BUREAU OF FISHERIES. 

REQUIREMENTS SATISFIED. 

After the first step was taken and the excellent result of rearing bottom- 
living animals in native water was recognized, it seemed most desirable to 
follow up the advantage gained in the rearing of other forms by extending and 
developing the procedure so that it would be applicable to pelagic fry. For- 
tunately we were able to hit upon a method which solved at once all the main 
difficulties arising from the peculiarities of pelagic existence of larvae and other 
free swimming animals. This method consists essentially of creating and 
maintaining within an inclosure of "native" water a gentle upward swirling 
current. It obviates the several difficulties which we have enumerated as 
peculiar to pelagic fry in the following ways: 

It effectually prevents the crowding of the fry to one wall of the car, for 
the force of the current carries them round and round continuously, nor can 
they work their way to the bottom, for the current has an upward as well as a 
rotary direction. Even the cannibalistic propensities, which are so pronounced 
in the larval stages of lobsters and some other animals, are rendered innocuous 
to a great extent by the forced separation of the fry and are mitigated by the 
availability of other food. 

The current being wholly internal, and its main component circular in its 
course, it does not force the fry strongly to one side nor allow them to remain 
in one place as does the tidal current passing through the inclosure. The 
pressure of the current against the sides varies, of course, with the rapidity 
with which the outside water is drawn into the car, with the extent of the area 
through which the water can pass out, and with the rapidity of the current. 
Since any or all of these factors can readily be controlled there is no difficulty 
in obtaining a proper adjustment of current for the requirements of particular 
cases. 

Stagnation is prevented even when no new water is admitted from the 
outside, for the water in the car is constantly being turned over and the lower 
strata brought to the top and aerated. When, therefore, the water of a car of 
considerable size is kept cool by being sunk into the ocean and shaded from 
the sun and is continuously forced to the surface so as to be relieved of waste 
gases as well as recuperated with oxygen, there is comparatively little need of 
continuous or frequent renewal. It is at least reasonable to suppose that, in 
what we may call (after Birge) the "respiration" of a small inclosed body of 
water containing a considerable quantity of animal life, the elimination of the 
waste or toxic gases is necessary, and that aeration which is accomplished by 
forcing more air into the water only partially fulfills the requirements of respi- 
ration. The analogv with the physiological process of respiration would seem 
to be real. In case of small, very thin, flat animals, where the ratio of surface 



A NEW PRINCIPLE OF AQUICULTURE. 765 

to the bulk is large, respiration may be continuous and direct without special 
internal apparatus, and, likewise, shallow water with a large expanse of surface 
has been found by experiment to need no aeration in order to maintain animals 
alive for a long time. On the other hand, in bulky animals, the respiratory 
apparatus provides always for the elimination of gaseous products of metab- 
olism as inevitably as it provides for the acquisition of oxygen. Therefore 
the bringing of the lower strata of water continuously to the surface fulfills 
two necessary requirements. 

For keeping larval forms which are not exceedingly minute, windows 
covered with screens about 16 meshes to the inch in the bottom of the cars 
allowing for intake, and similar ones in the sides for the exit of water, are satis- 
factory. A much finer mesh can be used in this case than would ordinarily be 
practicable, because the water is drawn in through the bottom screens with 
considerable force by the upward tendency of the current. It is possible by 
means of a filter device, which will be described hereafter, to hold fry which 
would pass through even very fine screens. 

The rotary upward current 'keeps the particles of food suspended in the 
water even when artificial food heavier than water is used. When, on the 
other hand, a pelagic live food is used, it is also, of course, readily available, 
because it is kept in motion and suspended. The important problem of the 
distribution of food for pelagic forms is solved by this method in a most satis- 
factory manner. 

ADAPTABILITY OF THE METHOD. 

Before describing the apparatus as at present installed at our station, 
where it is applied to the hatching and rearing of young fishes and inverte- 
brates, a word should be said to indicate its general adaptability to various 
requirements. In any protected body of water, whether river, lake, pond, or 
in the ocean itself, the apparatus can be quickly and cheaply installed. For 
experimental work the containing cars may be small. Dr. V. E. Emmel, by 
use of this method, succeeded for the first time in the difficult task of making 
mutilated lobsters of the first stage live to regenerate their appendages. His 
apparatus consisted of an ordinary "paper" bucket provided with screens and 
the apparatus for keeping the water in motion. On the other extreme the 
units in our regular installation at Wickford are square boxes measuring 10 
feet on a side and 4 feet in depth, with capacity approximately 12,000 liters 
(fig. 4, 5, 6, pi. xci, xcn). The capacity of a plant of this sort is capable of 
unlimited extension by the addition of units. At present the plant at Wickford 
has a capacity of 24 units of the size mentioned. The method is capable of 
application to aquatic animals, fresh water or marine, varying in size from 
those literally microscopic to those of a foot or more in length. We do not 



766 



BULLETIN OF THE BUREAU OF FISHERIES. 




A NEW PRINCIPLE OF AQUICULTURE. 767 

foresee that there are any strictly aquatic animals the requirements of whose 
young may not be fulfilled by means of this method. 

We have developed and applied the method mainly in connection with the 
hatching and rearing of larval lobsters, but we may assert, without fear of 
contradiction by anyone familiar with the rearing of lobster fry, that we have 
done this not because of the comparative ease of rearing lobsters. In the case 
of all species of fishes which we have attempted to rear the problem is easier 
than in the case of lobsters. 

APPARATUS. 

GENERAL DESCRIPTION. 

The apparatus as at present installed has proved capable of rearing the 
larval and young stages of fishes and of invertebrates belonging to several 
different groups. The main features are as follows: A houseboat consisting of 
two decked pontoons 4 by 4 feet square in section and 50 feet long held S feet 
apart, the intervening space decked and covered by two houses 10 by 10 feet 
square and 10 by 20 feet, respectively, flanked on either side by two floats 
attached to the houseboat and made of 6 by 6 inch spruce timbers bolted 
together and buoyed up by barrels. The spaces between the timbers of the 
floats are divided into areas 12 by 12 feet, to contain the hatching cars, and 
into alleyways about 2 feet wide, to contain the supporting barrels. (See 
diagram, p. 766, and fig. 1, 2, 3, pi. xc, xci.) 

The inclosures for confining the fry are in the form of 10-foot square boxes 
(fig. 5, pi. xcn) having two windows in the bottom and two windows in two 
sides, the windows screened, in the case of lobster fry and very small fishes, 
with fine-meshed woven bronze wire. 

In each box or car a pair of propeller blades, adjustable to various angles, 
are horizontally placed, attached to a vertical shaft with proper bearings (fig. 
4, pi. xci; fig. 6, pi. xcu; fig. 18, pi. xcviii). By the revolution of the pro- 
peller blades the water is kept in circular and upward motion (fig. 4) . The 
propeller shaft carries at its top a gear which engages a similar one with half 
the number of teeth borne on a horizontal longitudinal driving shaft. The pad- 
dle shaft can, however, be instantly thrown out of gear by a lever (fig. 22, pi. c). 
The longitudinal shaft transmits the power to all the propellers in one float 
(fig. 2, 3, and diagram). It receives its power from a shaft running trans- 
versely across the float, the two shafts being connected by mitered gears (fig. 4) . 
The transverse shaft of the float is connected to a similar one across the 
houseboat by a set of universal ball joints and an extensible shaft and sleeve 
device, invented for this particular purpose, which allows for several inches of 
variation in the length of the shafting system (rig. 17, pi. xcviii). The trans- 
verse shaft on the houseboat runs through the side of the house and inside the 



768 BULLETIN OF THE BUREAU OF FISHERIES. 

latter is connected with the engine by two sets of pulleys and belts which 
greatly reduce the speed (diagram, p. 766). 

A small gasoline engine furnishes the power. The engine speed of 324 revo- 
lutions per minute is reduced to about 36 revolutions per minute in the trans- 
verse shafting; then, by gears, to 18 revolutions in the longitudinal shafting, 
and to 9 revolutions per minute for the propeller blades within the boxes. 

Four horizontal driving shafts running lengthwise of the float are each 63^2 
feet long. The transverse shafts connecting these back to the engine have a 
combined length of 43 feet. The four large floats are only skeletons in struc- 
ture. Both they and the houseboat to which they are attached float upon 
the water and are subjected to considerable motion from the waves and from 
the swells of passing vessels. A too rigid construction, therefore, is not per- 
missible. Indeed, a friend of the station who is familiar with mechanical 
construction facetiously observed that any reputable engineer to whom we 
might submit the plans of our apparatus would without hesitation assert that 
it probably would not work. However, it runs continuously with hardly an 
hour of interruption for three or four months at a time. 

Several devices have been adopted which together make sufficient allowance 
for the inevitable rocking movement of the floats and for the warping of the 
light timbers, viz, comparatively light shafting (1 inch), which in long pieces is 
flexible; adjustable hangers; large-tooth cast gears; and the sliding shaft and 
universal joint which has been mentioned. No trouble with the running of 
the apparatus has ever arisen from the motion of the water, though the latter 
is sometimes strong enough to break out the screen windows. 

DETAILS OF STRUCTURE. 

Houseboat. — A brief description of the houseboat with its materials and 
dimensions is as follows: Two pontoons 52 feet long, 4 feet wide, and 4 feet 
deep, of 3-inch hard pine calked, completely decked with 2-inch hard pine 
calked; each pontoon with 3 bulkheads and 4 water-tight compartments acces- 
sible by hatches, painted all over, copper paint below water line; pontoons 
placed 8 feet apart securely fastened by crossbeams and heavy knees at each 
end; houses 10 by 10 feet near each end of the boat, with floors of 2-inch hard 
pine, roofs, sides, doors, shelves, closets, of North Carolina pine, painted out- 
side, natural-wood finish inside; roof of house 7 feet from floor and having a 
slight crown, covered with canvas and painted. An annex to the house (fig. 2, 
pi. xc) on one end, made of lighter material and of the same dimensions, has 
been added to give additional space for the engines and tools. 

Floats. — The four side floats, so-called, are merely skeleton rafts, buoyed 
with barrels, whose construction may be seen in the diagram and on plates 



A NEW PRINCIPLE OF AQUICULTURE. 769 

xci and xcii. Pieces of 6 by 6 inch timbers, spliced together if necessary, are bolted 
together to form a rectangle 19 by 75 y 2 feet. Parallel with the long sides and 
2]/^ feet inside are similar timbers, running the whole length of the raft. This 
makes an alleyway on each side for the supporting of barrels, and the spaces 
between the barrels are available for small rearing boxes used in preliminary 
experiments. Across the inner long timbers are placed 6 by 6 inch beams at 
intervals of 12 feet, dividing the whole raft into six compartments 12 by 12 
feet square for the reception of the rearing cars. Except for occasional spaces 
this completes the lower part of the raft. 

Upon these beams short vertical pieces are set at the corners of the car 
pools to form a rest for the seven upper crossbeams which run parallel with the 
lower ones (p. 766, and fig. 3, 4, pi. xci). These upper crossbeams of 4 by 6 inch 
stock support a longitudinal shaft beam, also 4 by 6 inches, which runs the whole 
length of the float through the middle and upon which are fastened the shaft 
hangers. 

The two floats on either side of the houseboat are fastened rigidly together 
with bolted timbers. The inside floats are attached to the houseboat by means 
of D irons and eyebolts to allow about a foot of up-and-down motion. The 
floats are built comparatively light and of cheap wood, in view of possible future 
change of plan as a result of experience. 

Rearing boxes. — The rearing boxes are square, made of 7 s-inch spruce 
tongued and grooved boards, nailed to a 2 by 3 inch frame with galvanized 
nails. The inside dimensions are 10 by 10 by 4 feet. The angles between 
adjacent sides and between the bottom and sides are truncated by boards 9 
inches wide and beveled on the edges (fig. 6, pi. xcii; fig. 13, pi. xcvi). The 
vertical corner frame pieces are left projecting above the top of the box about 2 
inches, to serve as corner posts for fastening the box in place. Ring bolts are put 
into the four lower inside corners of the box for use in raising the box for cleaning. 

Window cases 9 by 36 inches are placed on two opposite sides of the box 
to receive the movable window frames (fig. 6, pi. xcii; fig. 10, pi. xciv). Two 
similar removable window frames 22 inches square are placed in the bottom 
about 3 feet from the diagonally opposite corners of the box (fig. 6) . The size 
of the mesh in these screen windows varies, according to the size of the fry 
under experiment, from 16 to 2 meshes to the inch. The material is usually 
woven bronze or copper wire or galvanized "iron." 

In the middle of both sides of the box not having windows a broad slot is 
cut from the top to within about 8 inches from the bottom. It allows the box 
to be raised above the water, even though the shaft beam is low (fig. 5, 6, 
pi. xcii). When the box is down the doors (seen in fig. 9, pi. xciv), which are 
fastened on the side of the slot referred to, are fastened shut by strong outside 
buttons. 

B. B. F 1908 — 49 



770 BULLETIN OF THE BUREAU OF FISHERIES. 

It should be said here that this construction was adopted to save rebuilding 
the floats which had formerly held canvas bags, in which case the low shaft 
beam was not in the way. In the case of new construction, the shaft beams 
should be high enough to escape the box when the latter is raised out of the 
water (fig. 5, pi. xcii). 

The boxes are buoyant and have to be forced down into position, where 
they are held fast by two planks across the top at the end of the box (fig. 4, pi. xci) . 
The planks are mortised into the corner posts before referred to, so as to prevent 
lateral movement, and are fastened down to the beams of the float by heavy 
adjustable cleats secured by bolts (fig. 4, pi. xci; fig. 9, 10, pi. xciv). The 
boxes are painted inside and out. 

When a box is to be raised, the cleats are loosened, the planks removed, 
and ropes from the drums of a transportable windlass are hooked into the ring- 
bolts of the bottom corners (fig. 9 to 12). The doors are then opened and 
the hand windlass put into operation. One man has raised a box alone in 
fifteen minutes, and two men in five minutes. These boxes, the windlass, and 
many other things were designed and constructed by the superintendent, 
Mr. E. W. Barnes. 

Propellers. — The size and shape of propeller blades found to be most satis- 
factory vary according to the requirements of different fry. The form of those 
most used for lobster fry is shown in figures 6, plate xcii; 8, plate xciii; and 
18, plate xcviii. They consist of two wooden blades, each 4 feet 2 inches long 
and 8 inches wide at the base, tapered to 5 inches at the apex, and painted 
all over. Along the middle line the thickness is about 1% inches, but from this 
to either edge is a long bevel which leaves about l 2 inch at the edge (fig. 8). 
Each blade is fastened with iron straps to a piece of galvanized gas pipe, which 
is screwed into a four-way cross coupling (fig. 18). The latter admits also the 
vertical gas-pipe shaft running upward toward the gears and a short vertical 
steel shaft below which sets into a socket consisting of a short piece of large 
gas pipe fastened to the bottom of the car by a flange. This serves as a lower 
bearing or guard to the propeller shaft (fig. 18). 

The upper part of the propeller shaft is continued by means of couplings 
through the longitudinal shaft beam and carries a mitered gear at the top (fig. 14, 
pi. xcvi). In order easily to disconnect and take out the propeller a heavy iron 
sleeve coupling is inserted into the propeller shaft. The two pieces of the latter 
are held into the sleeve coupling by set screws (fig. 19, pi. xcix). As the set 
screws would be too heavy for galvanized piping, the lower part of the pro- 
peller shaft is continued upward by means of a piece of ordinary cold-rolled 
steel shafting (fig. 19). This is more easily shown in the figures than described. 

Driving shafts and gears. — The gear on the top of the vertical propeller shaft 
engages a similar gear with half the number of teeth on the longitudinal driving 



A NEW PRINCIPLE OF AQUICULTURE. 771 

shaft (fig. 21, 22, pi. c). The latter is supported above the shaft beam by adjust- 
able hangers. All the gears are east instead of cut and have large teeth (fig. 20, 
21,22). For our purposes they are probably more satisfactory, and are certainly 
much cheaper, than cut gears. A nice adjustment is not necessary, and the 
speed of all the shafting is low, being 36 to 18 revolutions for the horizontal 
shafts and 9 for that of the propeller. 

The longitudinal driving shaft connects by means of mitered gears to a 
transverse shaft running back toward the houseboat and engine (diagram, p. 766; 
fig. 4, pi. xci; fig. 20, pi. xcix). Between this and the transverse shaft of 
the houseboat is a pair of ball joints of the common type and the peculiar 
extension device referred to before (fig. 3, pi. xci; fig. 17, pi. xcvin). The lat- 
ter consists of a sleeve made of two heavy castings fitting loosely over two pieces 
of square shafting. The two sleeve castings are provided with flanges and are 
held together by screws, and, to avoid their accidentally slipping off into the 
water, one end is made fast to the shaft with set screws. Several holes are 
bored through the sleeve for convenience in oiling. This device allows the 
square shafting to slide back and forth in the sleeve easily and it has the 
advantage of being very cheap. It is also very strong, because the shaft has 
a bearing on the sleeve on all four of its surfaces. 

Shafting, pulleys, and engine on houseboat. — The transverse shaft on the 
houseboat connects with that on both pairs of side floats in the manner 
described, and is itself connected with the engine within the house by two 
sets of ordinary pulleys and belt drives in which the speed of the engine is 
greatly reduced. Two engines are set up ready to connect with the shaft, so 
that if either one gives out the other may be used. The engines are 1% to 3 
horsepower Fairbanks-Morse vertical type of gasoline explosion engines, and 
have proved exceedingly satisfactory. 

Boxes with filters for holding minute larva. — As a modification of the usual 
form of box or car, to be used for rearing larvae so small that they would go 
through any screen with meshes large enough to permit an adequate renewal 
of water, the following has been adopted: The ordinary boxes are carefully 
calked in all the seams, and their windows, save one of those in the bottom, 
are covered with canvas. A gravel and sand filter, made by putting about 4 
inches of gravel and sand into a shallow box with wooden sides and heavy gal- 
vanized ^-inch mesh wire in the bottom, is placed over the other bottom win- 
dow (fig. 21, pi. c). When the car is in place, an old-fashioned bucket chain is 
rigged on the longitudinal shaft, and the water is thus continually lifted and 
poured into the hatching box through a short trough. The buckets are painted 
with asphalt inside and the trough is lined with canvas to prevent contamination 
of the water from contact with metal or wood. The new water is added, there- 
fore, at the top of the box gradually — about t< 1 A gallons per minute (fig. 14, 
pi. xcvi; fig. 15, 16, pi. xcvn). 



772 BULLETIN OF THE BUREAU OF FISHERIES. 

The amount of water passing through the bottom of the filter does not 
create an appreciable outward current, and, at any rate, the fry are held above 
the bottom by the upward trend of the current created by the propellers. Two 
or three cars of this type have been operated for periods of four to ten weeks at 
a time. Several varieties of very young fishes and larval invertebrates have 
been reared with highly satisfactory results. Among the many hundreds or 
thousands of animals only three or four dead specimens of any kind have been 
observed. 

Canvas lining for boxes. — A further modification of this method has been 
adopted in order to prevent the escape of certain very small animals like crabs, 
which seek out and crawl into very narrow cracks in the wood. It consists of 
putting into the box a large canvas bag as a sort of lining and arranging the 
filter pump as usual (fig. 16, pi. xcvii). This apparatus has also proved 
satisfactory. 

POSSIBILITY OF VARIATION. 

So detailed a description of the apparatus as at present installed and in 
use might without a further word leave the impression that this apparatus alone 
fulfills the requirements of this general method of fish culture. On the con- 
trary, there is hardly a feature of the whole outfit that has not been represented, 
at one time or another during our experiments, by other materials or other 
forms. The present boxes, for example, have replaced bags of canvas and of 
scrim and bobbinet, not because the latter failed to give good results, but because 
they were less durable and otherwise objectionable. Three forms of power 
transmission have been operated successfully during the development of the 
plant. It is obvious that the gasoline "engine might under other circumstances 
properly give place to a different kind of motive power, such as steam or hot-air 
engines or electric, spring, weight, or water motors. For use in small experi- 
ments weight or spring motors, properly governed for speed, have much to 
recommend them, for individual cars could be independently operated in various 
localities without the inevitable expense and annoyances of running the engine 
and the apparatus for power transmission. 

PRECAUTIONS. 

There are, moreover, precautions to be taken in the construction of the 
cars and other devices. New wood, especially pine, and certain metals, par- 
ticularly copper and galvanized iron, which are frequently used as screens, are 
apt to injure, and often prove fatal to young animals even when under other 
circumstances the circulation through the car would be ample. A very striking 
instance of the effect of small quantities of copper and zinc-plated screening 
was furnished in an experiment made a year ago at our station by Dr. V. E. 



A NEW PRINCIPLE OF AQUICULTURE. 773 

Emmel in rearing fourth-stage lobsters to the fifth stage. Ninety fourth-stage 
lobsters were put separately into glass jars, one lobster into each jar, and the 
whole crate of jars submerged in the water about 2 feet below the surface. A 
screen of woven copper wire was placed over the wide mouth of each jar to keep 
the lobsters from escaping. All these lobsters were found dead twelve hours 
later. Galvanized copper wire screen was then substituted in a new experiment 
and in twenty-four hours the whole lot were dead. Finally a cloth screen of 
bobbinet was used, and out of 75 lobsters which were fed, only 1 died before 
moulting into the fifth stage. Of 15 which were not fed 4 died at the end 
of a month. These difficulties, if recognized, may in most cases easily be 
overcome. 

TESTS OF EFFICIENCY. 

The method and apparatus which have been herein described have been 
developed, as we have said, mainly in connection with the rearing of lobsters 
through their pelagic larval stages. But as proficiency in this work has increased 
we have come to realize that the method is equally well adapted to the rearing 
of a great variety of fishes and aquatic invertebrates. 

Hatching and rearing lobsters. — While the hatching of lobster eggs by this 
method presents no difficulties, and young lobsterlings, after reaching the fourth 
stage, can also be cared for without the use of special appliances, the larval 
lobsters, on the other hand, during the three free swimming stages of two or 
three weeks' duration, seem to incarnate nearly all the perverse and intractable 
characteristics which, from the view point of fish culture, are difficult to deal 
with. They are pelagic and are safe only when floating, yet in confinement 
they persistently tend to go to the sides and bottom of the inclosure. They 
are comparatively slow of movement and weak in their instincts of self-preser- 
vation and of seeking food, yet their most distressing characteristic is canni- 
balism. A method of artificial culture, therefore, which will successfully cope 
with the various difficulties involved in the rearing of larval lobsters might, a 
priori, be expected to answer the requirements of the culture of fishes, few of 
which, perhaps, offer so many difficulties. While the report on the special 
method of rearing lobsters is given in another paper, it may here be said, as 
indicating the general efficiency of the plant, that during the months of June 
and July and the first few days in August of this year we hatched and reared 
through their successive larval stages more than 320,000 lobsters (counted) by 
means of the apparatus as above described. 

Fishes incidentally reared. — While the apparatus was occupied with the 
rearing of lobsters, time and car space were not available for experiments on the 
rearing of fishes, but incidentally it was demonstrated that the young of many 
fishes would thrive and grow in the cars. Upon raising cars which had been 

a Report of Rhode Island Commissioners of Inland Fisheries for 1907, p. 104. 



774 



BULLETIN OF THE BUREAU OF FISHERIES. 



down for two or three weeks there were nearly always found in them a consider- 
able number of small fishes of various species. Since all the water of the car must 
in these cases have entered through the screen windows of -^ inch mesh, the 
fishes must have come in when they were very small. The following is an 
incomplete list of these fishes found in the cars. It should also be mentioned 
that among these fishes and the other ybung specimens placed in the cars there 
was no evidence of illness or mortality. 



Species. 


Size. 


Dates. 


Species. 


Size. 


Dates 




Mm. 






Mm. 




Mummichog (Fundulus 


5-25 


Thro u gh u t 


Puffer (Sphcroides mac- 


4 


(?) 1908. 


sp.) 




season of 


ulata). 


3-5 


July 9, 1908. 






1907 and 




18 


Aug. 3, 1908. 






1908. 


Flatfish (Pseudoplcu- 


10-21 


From about 


Sil versifies (Menidia 


4-21 


June 27 to July 


ronectes americanus) . 




June 15 to 


sp.) 




8, 1908. 






about July 


Hake ( Urophyc is sp. ) _ . 


28 


July 26, 1907. 






1, 1908, from 


Pipefish (Siphostoma 


15 


July 6, 1908. 






10 to 50 were 


juscum). 


30 


Aug. 6, 1908. 






found in 




114 


Aug. 7, 1908. 






every car 




77 


Do. 






when raised 




144 


Aug. 8, 1908. 


Tautog (Tautoga onitis) 


3- 2 


July 8, 1908. 




66 


Aug. 21, 1908. 




4.8 


July 9, 1908. 




73 


Do. 




20 


July 25, 1908. 


Kingfish (Menlicitrhus 


41 


Aug. 4, 1908. 




1 1 


July 28, 1908. 


saxatilis). 








20, 18 


Aug. 3, 1908. 


Squeteague (Cynoscion 


4- 2 


July 23, 1908. 




20, 24 


Aug. 4, 1908. 


regalis). 


19 


July 30, 1908. 




12.5 


Aug. 7, 1908. 




12.5 


July 28, 1907. 




8,9 


Aug. 9, 1908. 




6-5 


Do. 




23. 25 


Aug. 10, 1908. 




25 


Aug. 8, 1907. 




21, 41 


Aug. 1 1, 1908. 




18 


Do. 




8 


July 28, 1907. 




20 


Aug. 9, 1907. 




5-5 


July 25, 1907. 




29 


Aug. 13, 1907. 










3i 


Do. 










37 


Aug. 26, 1907. 









From July 6 to the last of August, 1908, small anchovies (Stolephorus 
mitchclli) continually entered the cars through the fine screens. In many 
instances hundreds of them, from 2 to 20 millimeters long, were found in these 
cars. In August several cars were fitted out with coarse screens, one-fourth 



"From data collected by H. C. Tracy. 



A NEW PRINCIPLE OF AQUICULTURE. 775 

inch mesh, and several thousands of anchovies entered one of the cars in a sin- 
gle night. Within the cars they lived and grew. Great numbers of very small 
specimens between 2 and 10 millimeters in length were taken in July. Mr. 
Tracy points out a fact of particular significance, namely, that in the tight filter 
cars many specimens from 2 millimeters to 8 millimeters were found which 
must have been dipped up by the chain of buckets as eggs or as very small fry, 
since the fry of 10 millimeters are so quick and wary that they would hardly be 
caught in this way. There is no doubt whatever that the young anchovies of 
all sizes thrive perfectly well in the cars provided with screens, and also in the 
filter cars, and it is more than probable that the eggs of this species frequently 
hatched in the cars. 

About 20 anchovies placed in one of the filter cars on July 28, 1908, were 
doing well at the date of writing (September 19, 1908), and showed a very con- 
siderable growth. 

Hatching and rearing fishes. — Near the end of the season for rearing lobsters, 
during the latter part of July, when the pressure of other work was relieved, 
some of the large cars were reserved for definite experiments to test the practi- 
cability of the method and apparatus as applied to the hatching and rearing of 
fishes. Unfortunately at this time of the year there were comparatively few 
fishes whose eggs we could obtain, and we were unable, therefore, to exercise 
much choice in our material. 

On July 17 a quantity of eggs of the "silverside" (Menidia) were obtained, 
and, after being fertilized, were put into a car with the filter and bucket-chain 
rigged as already described. A short-bladed paddle was used like that in figure 
22. This was hung about 2 feet from the bottom, the lower bearing being 
dispensed with. 

The egg masses were teased apart into small clusters and placed on a piece 
of cloth mosquito netting which was tacked to a piece of soaked wood, so as to 
form a bag, and suspended in the water. The bag thus formed was held extended 
and kept from collapsing by a coiled piece of insulated electric wire on the 
inside. (Practically the same method has been used very successfully in the 
hatching of the flatfish, Pscudopleuronectes.) The eggs hatched in about ten 
days with apparently no mortality. The young fishes readily escaped through 
the netting and seemed to thrive perfectly well in the car, where they were kept 
until August 21, when they were transferred to another similar car, which, 
however, had a canvas lining. Here they have continued to live until the date 
of writing (September 19, 1908). There has been no evidence of mortality of 
any kind during the experiment, although little attention has been given to the 
feeding, and the fry have had to depend upon the living pelagic food which 
entered with the water from the chain of buckets. 



776 



BULLETIN OF THE BUREAU OF FISHERIES. 



From the time of hatching to the transference of the fry to another car 
specimens were taken out daily and preserved. The average daily measure- 
ments are here given : 



July 26 3.85 

July 27 4.86 

July 29 5.82 

July 31 6. 2i 

August 1 6.90 

August 2 719 

August 3 7.68 



Mm. 

August 4 7-9° 

August 5 7.70 

August 6 7-76 

August 7 8.32 

August 8_- 8. 00 

August 9 7-98 

August 10 8.23 



August 1 1 8.22 

August 12 8. 80 

August 13 9. 20 

August 14 8.77 

August 15 9.30 



On the afternoon of July 27 a portion of the eggs which had remained 
unhatched in the experiment thus described were transferred to another simi- 
larly rigged rearing car (known as S 4) , and these eggs hatched within the next 
day or two. The measurements of specimens taken daily from this new car com- 
pare in an interesting way with those given in the previous table. Although they 
came from the same batch of eggs, and differed only in being slightly younger, 
they grew more rapidly than the first lot and soon so far outstripped those in 
the original car that the difference was noticeable upon casual observation. 

This difference was doubtless due to the fact that the second lot had more 
to eat because there were fewer specimens in the car, for, as we have said, the 
fry had to depend for their food upon the pelagic fauna. By towing in these 
cars with a small bolting cloth net the absence of copepods and larval animals 
was conspicuous, especially when compared with the towings taken from a neigh- 
boring control car which was in all respects similarly conditioned except that it 
supported no young fishes. In the latter the pelagic life was abundant. It 
was evident that the swarm of young fry used up the supply of pelagic food as 
fast as it came into the car. 

The following table gives the daily average length of specimens of Menidia 
in this second experiment : 



July 27 4 

July 28 4 

July 29-- 5 

July 30 6 

July 31-- 5 

August 1 6 

August 2 7 



August 3 7.76 

August 4 8.72 

August 5 9.00 

August 6 9. 98 

August 7 9.82 

August 8 10. 02 

August 9 9.25 



Mm. 

August IO IO.04 

August 11 io- 34 

August 12 10.12 

August 13 10. 74 

August 14 10.21 

August 15. 11.72 

August 17 10.26 



The regular measurements were discontinued after this date. On Sep- 
tember 8 the average measurement was 14.83 millimeters and on September 14. 
14.45 millimeters. In all of these measurements different groups of individuals 
were caught up, and the averages, therefore, seem to show a decrease in size 
rather than an increase when there is not considerable rapidity of growth. 



A NEW PRINCIPLE OF AOUICULTURE. 



777 



A few eggs of Fundulus heteroclitus were fertilized on July 27 and were 
placed in the original filter car. They were floated near the surface in a shallow 
bag of netting somewhat similar to that described in the case of Menidia. The 
eggs hatched on August 5 and 6 and the fry all lived in healthy condition until 
they were taken out at intervals and preserved. The daily averages of length 
for the first ten days are as follows: 



Mm, 

August 9 5.56 

August 10 5.37 

August 11 5.88 

August 12 5-92 



August 13 5.98 

August 14 6.25 

August 15 6. 30 



August 5 4.92 

August 6 5.07 

August 7 5-4° 

August 8 5.35 

Specimens of this lot have continued to live in one of the cars until the 
date of writing (September 19). 

On July 17, 56 young toadfish, measuring from 15 to 17 millimeters, which 
had been raised from the eggs in a small car, were transferred to the original 
filter car. At more or less irregular intervals during the next four or five weeks 
specimens were taken out and measured. The following table of individual 
and average measurements indicates the rate of their growth : a 



Mm. 



July 17 (56 specimens) 15. 0-17. o 

July 30 19.0 

July 31 22.5 

August 1 18.7,22.0 



Mm. 

August II 26.0 

August 14 26.5 

August 21 619. 0-33. 7 



In order to test these cars with as many kinds of fishes as possible, we 
introduced the young of some other species in lieu of fish eggs, which could not 
be obtained in great variety at this season of the year. On July 17 a lot of 
pipefish taken from the brood pouch of a male were put directly into the original 
filter car. The individuals appeared to be of practically equal length and 
measured 10 millimeters. They apparently all lived and, like the other speci- 
mens in the cars, continued to thrive, showing no sign of disease, until they 
were taken out, on August 21. 

The following data show the rate of growth as indicated by the average 
sizes at the end of irregular periods. No food was given to them except that 
which came in with the water by means of the chain of buckets. 



July 17 10. o 

July 18 11. 4 

July 20 21.8 

July 23 . 24.5 

July 25 27.5 

July 27 _ 26.5 



Mm. 



July 30 44.0 

July 31 46.1 

August 2 52.6 

August 6 61.6 

Augusts 58.6 

August 11 67.4 



August 15 67.2 

August 20 69. 4 

September8 c 7 I -3 

September 14 C70.0 



I am indebted for these measurements to Mr. H. C. Tracy. 

b Average, 30.21 mm. Fifty-four specimens out of 56 put into the car were recovered. 

c Measurements taken after transference to new car. 



778 BULLETIN OF THE BUREAU OF FISHERIES. 

On August 21 the remaining specimens were transferred to another filter 
car with canvas lining, where they remained alive and well up to September 19. 

On July 21 another pipefish was caught with a brood pouch full of young 
which measured 10 millimeters. These young were placed, together with the 
second lot of Menidia, in a filter car rigged with a chain of buckets like the 
original one. These specimens lived and thrived equally well. No food was 
given them except on one or two occasions. The data of growth are as follows : 



Mm. Mm. Mm. 



July 23 10.7 

July 27 19.0 

July30_-_ ^4° 

August 3 1 3 1 ■ 4 



August 6 37.8 

August 8 41.8 

August 11 4 1 . 9 

August 15 45- 



September 8 59. o 

September 14 62.8 



On August S and 10 a number of young bluefish were caught in the seine 
and were placed in one of the rearing cars which had been provided with coarse 
window screens of l /\ inch mesh. When put into the car there were already 
present in the water several thousand young anchovies, about 20 to 25 milli- 
meters in length. These the bluefish ate during the first day. On several 
occasions a few Menidia and Fundulus were given them to eat. On August 
1 2 they were given as much raw meat as they could eat, and this they devoured 
ravenously. They were fed on meat again on August 15 and on Menidia two 
days later. The average size of these bluefish on August iS, about ten days 
after they were put into the car, was 140.8 millimeters, an average increase of 
about 10 millimeters. On September 1 they were measured again, having 
been fed meantime on several occasions with Menidia, Fundulus, and other 
small fishes. The average length on this date, September 1, was 174 milli- 
meters. This measurement and the two which follow were taken from the 
nose to the end of the fin rays, whereas the previous measurements were taken 
from the nose to the base of the fin rays. Between September 1 and Sep- 
tember 8 the specimens were not fed. On September 8 they measured 175.1 
millimeters, showing an increase during seven days of 1.1 millimeters. 

On September 8 a quantity of live fishes was put into the car to serve 
as food for the bluefish, and during the next seven days the bluefish showed 
an average growth of about 10 millimeters, the average length being 184.3 
millimeters. 

The filter cars which have been described, and in which the previously 
mentioned eggs and young fishes were kept alive, have also proved themselves 
capable of maintaining a considerable variety of other fishes and invertebrates, 
among which are the following: Tautog, flatfish, anchovy, oysters (both old and 
young) , scallops, anomia, crabs, barnacles, polyzoans, Botryllus, Nereis larvae, etc. 

Crabs and scallops. — On August 2, 1908, a very large number of zoeae and 
megalops of the oyster crab were found floating at the surface of the water. A 



A NEW PRINCIPLE OF AQUICULTURE. 



779 



considerable number were caught with a net and transferred to one of the filter 
cars, in which they have remained ever since. On September 19 their average 
measurements were, length 8 5 -s millimeters and breadth 10^ millimeters (Mr. 
Sullivan) . 

On August 3, 13 scallops, measuring between 45 and 65 millimeters in 
length, were placed in the second filter car after having a deep notch filed in the 
shell so that the rate of their growth could be determined accurately. On 
September 18, 11 of these specimens were taken out of the car and were in 
excellent condition. The notch and the zone of new growth indicated precisely 
the size and shape of the shell when the scallop was placed in the box. The 
increase in length was about 20 per cent. The following table gives the measure- 
ments of these specimens: 



Length. Aug. 3. 


Length, Sept. 18. 


Length. Aug. 3. 


Length, Sept. 18. 


Mm. 


Aim 


Mm. 


Aim. 


5° 


60 


51 


60 


4+ 


55 


s 2 


64 


47 


60 


46 


56 


60 


68 


5^ 


62 


45 


55 







GENERAL APPLICATION OF THE METHOD IN AQUICULTURE. 

There are two great problems in the general question of fish culture to the 
solution of which the method herein described contributes: 

First, to the problem of hatching and rearing to an optimum size for libera- 
tion quantities of fishes of economic value for the direct purpose of stocking the 
waters. The comparative ease of hatching eggs of most fishes has resulted in 
the establishment of many prolific hatcheries; on the other hand, the number 
of establishments capable of rearing young fishes and the number of species so 
reared in confinement are few. A method of culture, therefore, which is capable 
not only of hatching but of rearing large numbers of fishes of widely different 
species marks, we hope, a new step in fish culture. 

The second general problem is the ascertainment of the appearance, habits, 
requirements, and rate of growth of economically important fishes in their earlv 
stages of post-embryonic development. As contrasted with the vast amount 
of investigation of the embryonic stages of development, which has been 
facilitated by the abundance of readily available material in the form of eggs of 
all stages, the data relating to the post-embryonic development are almost 
entirely lacking. Even the identification of the voung of many food fishes 
abundant in their spawning season is at present impossible. A method by 



780 BULLETIN OF THE BUREAU OF FISHERIES. 

which eggs of widely different species may be hatched and reared and by which 
the unidentified fry caught at large may be reared under observation will be 
able, we hope, to furnish the necessary material for the solution of this general 
problem. 

APPLICATION IN TRANSPORTATION OF LIVE FISHES. 

In our opinion the essential principle upon which this method of fish culture 
is based will be found of value in solving the problem of the transportation of 
live fishes and, moreover, the method and even a portion of the apparatus 
can be modified and adapted so as to carry this principle into effect. The 
principle, is, briefly, to provide at the start native "unmodified" water; to 
maintain a proper temperature and density, and in some cases current; to 
secure the continuous "respiration" of the water, including the egress of waste 
gases of the metabolism of contained fishes and often of bacteria as well as the 
access of oxygen, and to avoid contact with injurious metallic substances. 

To carry into effect this principle we propose the following method : To use 
for transportation an iron tank enameled on the inside with a vitreous substance 
in order to prevent contact of the water with the metal; to use only water 
dipped from the water in which the animals have been living, in order to insure 
its proper constitution; to surround the tank with a jacket into which ice or 
warm water can be put to control the temperature (for many animals, at any 
rate, both among fishes and invertebrates, we have found by experience that a 
low temperature is a very important factor in maintaining life when the animals 
are crowded into a small amount of unrenewed water) ; to provide both the 
current and the continuous respiration by installing a propeller device of 
enameled iron kept in motion by means of a spring motor. 



Bri.. U. S. B. F., r 9 o8. 



Plate XCI. 




v *£2^ 




! n ; —Starboard side, looking aft. inside float. Shafting system and general 
arrangement of cars. 




Fig. 4.— Car with propeller in motion. From propeller the shafting may be followed back | i-S) 
to the universal joint. 1, propeller shaft; 2. sleeve coupling; ,5, longitudinal shaft; 4, adjust- 
able shaft hanger; 5, gear trains from longitudinal to transverse shafts; 6, transverse hori- 
zontal shaft of float; 7, shaft hanger; 8, ball joint connecting shaft with that of house boat; 
9, edge of rearing box; 10, brace across corner of rearing box; 11, holding-down plank 
mortised into corner post; 12, shaft beam. 



Bul. U. S. B. F., 1908. 



Plate XCII. 




Fig. 5. — Rearing car raised and held Tip by portable windlass. 1, slot in end «>f car through 
which the longitudinal shaft run- when car is raised; 2, longitudinal shaft; 5, side window of 
car; 4, portable "horse" and windlass. 




Fig. 6. — Interior of rearing car, and propeller, 1, slot in end of car; 2, doors for closing the slot; 
3, side screen windows; 4 and 5, bottom windows; 6, box covering gear trains; 7. ' ransvi 1 se 
shaft; 8, longitudinal shaft; 9, towing car. The arrangement of shafting on farther float can 
be seen. 



Bru. U. S. B. F., 1908. 



Plath XCIII. 




FIG. 7.— Lifting the disconnected propeller out of the water. The upper por- 
tion of tin* shaft with the sleeve coupling is seen at i. 




Fig. S. — The propeller removed, showing disconnected shaft. The upper part of the shaft and 
the coupling are faintly visible under the shaft beam. The photograph shows well the size 
and shape of the propeller blades. 



Bul. U. S. B. P., 1 90S. 



1'i.atk XCIV 




Fig. '-.—Cleat at the end of (he holding-down plank, 
sh« wing the detail 1 1 ). 




Fig. 10.— The cleats being removed, the car rises part wav by its own buoyancy. Opening doors 
of the slot at end of car to admit the longitudinal shaft beam allows the car to be entirely 
raised- 1, cleat; 2. holding-down plank 1 longitudinal shaft beam; 4 and 5, side windows 



Bul. U. S. B. F., 1908. 



Plate XCV. 




Fig. 11.— Interior of rearing car. Preparing to calk small cracks before lowering the car. 
I, side window; 2, end slot; 3, doors for same; \, buttons to hold doors shut; 5 and 6, the trans- 
verse shaft, universal joint, and sliding sleeve; 8, exhaust and muffler. 




-Raising the car by means of windlass. Ropes from the drums nf the windlass are 
fastened by hooks to rings in the lower corners of the car. 



Bul. U. S. B. F., 1 90S. 



Plate XCVI. 





Bri.. U. S. B. F., 1 90S. 



Plate XCVII. 




Fig. 15.— 1-ilter car, same as figure 14, plate xcvl, showing bucket chain in 
operation. One oi the buckets has just emptied itself and the stream of 
water is faintly shown running into the trough. 




FIG 16.— Filter car with canvas lining. Chain buckets on left. The propeller blades 
may be seen iu the water. 



Bui,, U. S. B. F., 1908. 



Plate XCVIII. 




FiG. 17. — Detail of device fur extension and universal movement. 1, adjustable shaft hanger on 
house boat; 2, ball joint; 3, square shafting, fastened by set screw- mtn ball joint at leit, and 
also 14) int " sleeve; 4 and 5, screws through flanges of sleeve; 6, oil holes; 7. square shaft which 
slides iu and out of sleeve; S, shaft hanger upon side float. 




Fig. iS.— Detail of lower portion of the propeller shaft and its socket in floor 
of car. 1, propeller shaft, made of gas pipe; 2, short portion of shaft 
made of steel, to fit into the socket (6); 3, four-way pipe coupling; 4, gas 
pipe to which blades are strapped; 5, strap holding propeller blades; 6 
and 7, socket and flange; 8, upper disconnected .-teel portion of the pro- 
peller shaft; 0, shaft beam; 10, window in bottom of car; u, base of 
propeller blade, showing in section the shape. 



Bul. U. S. B. F., 1908. 



Pi.atk XCIX. 




KlG. 19.— Detail 1 if propeller shaft couplings. 1, underside of shaft beam; 3, upper steel portion 
1 if shaft, which hears gear on top and inter- sleeve coupling below; 1 cast sleeve coupling; 
5, set screws holding shafts in coupling; 6, short piece of steel shaft; 7, pipe coupling; 8, lower 
part of shaft, made of pipe; 9, measuring stick, made of sections 6 inches long. 




1 i<. io —Detail of gears on float at junction of transverse and longitudinal shafts. (Compare 
fig. 4, pi. xci.) 1, gear on horizontal shaft from house boat; 2. large gear on longitudinal 
shaft, reducing speed one-hall, ; . gear on the inner end of transverse shaft (4); 4 shaft 
transmitting power to outer float; 5, longitudinal shaft on inner float; 6 oil box 



Bul. U. Sf B. F., 1908. 



Platk C. 




o-c 



« ! 



O rt 5 

5 bo'Bi 









I.S «< 




bin 
o 5- 



o.s 



